Commercial emulsions containing an amine functional polydimethylsiloxane fluid are limited in their market appeal as they are known to contain only relatively low viscosity amine functional polydimethylsiloxane fluids.
In addition, these commercial emulsions may often contain in excess of about one percent of a volatile cyclic species of polydimethylsiloxane such as octamethylcyclotetrasiloxane, in addition to the low viscosity amine functional polydimethylsiloxane fluid, and this content of volatile species is unacceptable according to recent safety and environmental regulations and guidelines.
While higher viscosity polysiloxane polymers with a content of volatile cyclic species less than 0.5 percent have been obtained by reacting certain polysiloxanes with a crosslinking agent in the presence of a catalyst, such chain extensions have been obtained using an OH endblocked PDMS and a dialkoxysilane. This procedure is very slow and often takes weeks in order to reach completion. When such processes have been attempted to be modified in order to speed up the reaction, the use of a trialkoxysilane instead of a dialkoxysilane has led to the production of crosslinked elastomeric materials which are undesirable in many applications.
Where the prior art does refer to an emulsion containing an amine functional polydimethylsiloxane, the patents are either silent as regards the particular viscosity or molecular weight of the amine functional polydimethylsiloxane fluid contained in the emulsion, or where the viscosity or molecular weight of the amine functional polydimethylsiloxane fluid is mentioned, it is significantly below the levels now required in the personal care arena industry-wise. In patents where a higher viscosity or a higher molecular weight of the amine functional polydimethylsiloxane fluid is mentioned, however, the patents are generally silent as to how the emulsion is prepared. One example is U.S. Pat. 5,326,483 (Jul. 5, 1994).
In any event, although the prior art known to applicants is replete with patents relating to various types of cured systems containing high viscosity and high molecular weight polysiloxanes, it is not believed to be generally know to employ a trialkoxysilane in order to polymerize an OH endblocked PDMS in bulk, and to produce by such a procedure, a high molecular weight linear non-crosslinked silicone polymer in emulsion form. This is the essence of the contribution of the present invention.
Moreover, it is not believed to be generally know to conduct a polymerization, and then to interrupt the process of polymerization by addition of an anhydride and emulsification, particularly in this silicone cure system, which is known to be unstable and subject to reversion, i.e., depolymerization or post polymerization. However, by the addition of a low level of a carboxylic anhydride directly into the silicone polymer prior to its emulsification, applicants herein have discovered an efficient means avoid this type of reversion.